CN101572682A - Method and device for acquiring channel information - Google Patents
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Abstract
The invention provides a method and a device for acquiring channel information. The method mainly comprises the following steps that: a transmitting terminal sends downlink pilot frequency information to a receiving terminal and receives a mixed pilot frequency returned by the receiving terminal, wherein the mixed pilot frequency is acquired by multiplying the received downlink pilot frequency by an orthogonal code and then superimposing the result with an uplink pilot frequency by the receiving terminal, and the orthogonal code only corresponds to the receiving terminal; and the transmitting terminal performs estimation on uplink channel information according to uplink pilot frequency information in the mixed pilot frequency, and performs estimation on downlink channel information of the receiving terminal according to the estimated uplink channel information and downlink pilot frequency and orthogonal code information in the mixed pilot frequency. By using the method and the device, the transmitting terminal can accurately acquire the uplink and downlink channel information under the condition of not increasing extra feedback signaling overhead.
Description
Technical Field
The present invention relates to the field of wireless communications, and in particular, to a method and an apparatus for acquiring channel information.
Background
A schematic diagram of the transmission and reception process of a wireless communication system is shown in fig. 1. In a wireless communication system, a transmission signal is affected by a physical transmission channel during transmission, fading and distortion may occur, and a receiving end generally needs to estimate the physical transmission channel in order to recover the transmission signal, and the influence of the physical transmission channel on the transmission signal is eliminated through equalization processing. The effect of the above equalization process is affected by noise, for example, a zero-forcing equalizer may cause noise amplification in case of a low signal-to-noise ratio, and an MMSE (Minimum Mean Square Error) equalizer may effectively suppress the influence of noise, but needs to estimate the variance of noise at the receiving end.
In order to solve the influence of noise on the equalization processing at the receiving end, a transmitting end usually performs preprocessing on a transmitting signal according to the characteristics of a physical transmission channel, that is, a Single Input Single Output (SISO) system performs pre-equalization on the signal, and a Multiple Input Multiple Output (MIMO) system performs pre-coding on the signal. The preprocessing of the transmitting end can improve the fading of signals, avoid the amplification of noise when the receiving end processes deep fading channels, and greatly reduce the complexity of signal processing of the receiving end.
The transmitting end preprocesses the transmitted signal and needs to know the state information of the downlink channel, so that the receiving end needs to estimate the state information of the downlink channel and correctly feed back the state information of the downlink channel to the transmitting end.
A first method for a receiving end to feed back state information of a downlink channel to a transmitting end in the prior art is as follows: a receiving end (for example, a terminal) estimates downlink Channel parameters according to downlink pilot frequency, calculates an optimal precoding matrix for the receiving end according to the downlink Channel parameters, and then feeds back an index number of the optimal precoding matrix, a rank of a downlink Channel, and Channel Quality Indication (CQI) information to a transmitting end, and the transmitting end (for example, a base station) performs precoding on a transmitting signal according to the information fed back by the receiving end.
The first method for the receiving end to feed back the state information of the downlink channel to the transmitting end in the prior art has the following disadvantages: the receiving end needs to calculate according to the estimated downlink channel parameters, and selects the optimal codebook, thereby increasing the calculation burden of the receiving end. The number of codebooks of the precoding matrix is limited, and quantization errors of the codebooks exist, and the errors can greatly affect the performance of precoding processing at a transmitting end. If it is to be ensured that the transmitting end can obtain sufficient downlink channel state information, the uplink feedback signaling overhead is huge.
A second method for a receiving end to feed back state information of a downlink channel to a transmitting end in the prior art is as follows: a direct channel feedback method. A receiving end (for example, a terminal) estimates downlink channel parameters after receiving a downlink pilot signal, then encodes the estimated downlink channel parameters, and sends the encoded downlink channel parameters and an uplink pilot to a base station, wherein the encoded downlink channel parameters and the uplink pilot are frequency-divided. After receiving the uplink signal, a transmitting end (e.g., a base station) estimates uplink channel parameters by using an uplink pilot, and then recovers the downlink channel parameters by using the estimated uplink channel parameters.
The second method for the receiving end to feed back the status information of the downlink channel to the transmitting end in the prior art has the following disadvantages: the encoded downlink channel parameters need to occupy special time-frequency resources and are fed back to a receiving end.
Disclosure of Invention
The embodiments of the present invention provide a method and an apparatus for acquiring channel information, so as to solve the problems that the prior art needs to increase the computation burden of a receiving end, needs to occupy special time-frequency resources, and the like.
The purpose of the embodiment of the invention is realized by the following technical scheme:
a method of acquiring channel information, comprising:
a transmitting terminal sends downlink pilot frequency information and receives a mixed pilot frequency returned by a receiving terminal, wherein the mixed pilot frequency is obtained by multiplying the received downlink pilot frequency by an orthogonal code and then overlapping the uplink pilot frequency by the receiving terminal, and the orthogonal code is uniquely corresponding to the receiving terminal;
and the transmitting terminal acquires uplink channel information according to the uplink pilot frequency information in the mixed pilot frequency, and acquires the downlink channel information of the receiving terminal according to the uplink channel information and the downlink pilot frequency and orthogonal code information in the mixed pilot frequency.
A method for processing pilot frequency information comprises the following steps:
receiving downlink pilot frequency information sent by a transmitting terminal, multiplying the downlink pilot frequency by an orthogonal code, and then superposing the downlink pilot frequency with an uplink pilot frequency to obtain a mixed pilot frequency, wherein the orthogonal code is uniquely corresponding to the receiving terminal;
and sending the mixed pilot frequency to the transmitting end.
A channel information acquisition apparatus comprising:
the pilot frequency sending and receiving module is used for sending downlink pilot frequency information to a receiving end and receiving mixed pilot frequency returned by the receiving end, wherein the mixed pilot frequency is obtained by multiplying the received downlink pilot frequency by an orthogonal code and then overlapping the multiplied downlink pilot frequency with uplink pilot frequency by the receiving end, and the orthogonal code is uniquely corresponding to the receiving end;
and the channel information acquisition module is used for acquiring uplink channel information according to the uplink pilot frequency information in the mixed pilot frequency and acquiring the downlink channel information of the receiving end according to the uplink channel information and the downlink pilot frequency and orthogonal code information in the mixed pilot frequency.
A pilot information processing apparatus comprising:
the mixed pilot frequency acquisition module is used for receiving downlink pilot frequency information sent by a transmitting end, multiplying the downlink pilot frequency by an orthogonal code, and then superposing the downlink pilot frequency with an uplink pilot frequency to obtain a mixed pilot frequency, wherein the orthogonal code is uniquely corresponding to the receiving end;
and the mixed pilot frequency transmission module is used for sending the mixed pilot frequency acquired by the mixed pilot frequency acquisition module to the transmitting end.
It can be seen from the technical solutions provided by the embodiments of the present invention that the embodiments of the present invention can enable a transmitting end (base station) to correctly acquire information of uplink and downlink channels without adding extra feedback signaling overhead. And the processing complexity of a receiving end (terminal) is greatly reduced, and the signal is favorably pre-equalized or pre-coded at a transmitting end.
Drawings
Fig. 1 is a schematic diagram of a process for transmitting and receiving in a wireless communication system;
fig. 2 is a schematic diagram of a processing procedure of data transmitted by a base station in embodiment 1 of the present invention;
fig. 3 is a schematic diagram of a processing procedure of receiving and processing a signal by a terminal in embodiment 1 of the present invention;
fig. 4 is a schematic diagram of a processing procedure after a base station receives data returned by a terminal in embodiment 1 of the present invention;
fig. 5 is a schematic structural diagram of an embodiment of a channel information acquiring apparatus according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of an embodiment of a pilot information processing apparatus according to an embodiment of the present invention.
Detailed Description
In the embodiment of the invention, a transmitting terminal sends downlink pilot frequency information to a receiving terminal, the receiving terminal multiplies the downlink pilot frequency by an orthogonal code, then superposes the downlink pilot frequency with an uplink pilot frequency to obtain a mixed pilot frequency, and the mixed pilot frequency is transmitted to the transmitting terminal. The orthogonal code is uniquely corresponding to the receiving end, when a plurality of receiving ends exist, the orthogonal codes of different receiving ends are orthogonal, and the uplink pilot frequencies of different receiving ends are orthogonal.
And the transmitting terminal estimates the uplink channel information according to the uplink pilot frequency information in the mixed pilot frequency, and estimates the downlink channel information of the receiving terminal according to the estimated uplink channel information and the downlink pilot frequency and orthogonal code information in the mixed pilot frequency.
In practical application, when the number of the uplink pilots of the receiving end is greater than the number of the downlink pilots, the receiving end may use a plurality of uplink pilot resources to repeatedly transmit the mixed pilot signal or use a plurality of uplink pilot resources to transmit the mixed pilot signal after encoding the downlink pilots. The receiving end can also estimate a downlink channel at the downlink pilot frequency by adopting a minimum mean square error channel estimation method, multiply the information of the downlink channel by the orthogonal code, and obtain the mixed pilot frequency after the information is superposed with the uplink pilot frequency. The receiving end can also transmit the mixed pilot signal to the transmitting end for multiple times, each transmission respectively occupies part of the uplink bandwidth, and part of the mixed pilot signal is respectively transmitted.
The downlink pilot frequency and the uplink pilot frequency can be composed of a plurality of sequences, and each sequence occupies a segment of narrow-band bandwidth.
Embodiments of the present invention are described in detail below with reference to the accompanying drawings.
Embodiment 1, in this embodiment, multiple terminals multiplex uplink pilots in a CDM (CODE division multiplexing) manner, and the uplink pilots of the terminals are orthogonal to each other. The processing procedure of the data transmitted by the base station in this embodiment is shown in fig. 2, and the specific processing procedure is as follows:
the base station firstly performs coding modulation and pre-equalization processing on a signal to be transmitted, inserts downlink pilot frequency into a frequency domain of the processed signal, performs OFDM (orthogonal frequency division multiplexing) modulation on the signal, adds a CP (Cyclic Prefix), and then transmits the signal through a physical transmission channel.
The processing procedure of receiving and processing the signal by the terminal in this embodiment is shown in fig. 3, and the specific processing procedure is as follows:
the data transmitted by the base station is transmitted by a physical transmission channel and then received by the terminal. It is assumed that downlink antennas of the base station are configured to be M × N, i.e., M is the number of transmit antennas of the base station, and N is the number of receive antennas of the terminal. After the terminal performs CP-passing and OFDM-demodulation on the received signal, the obtained downlink pilot signal is:
Yi(k′)＝Hdl，i(k′)·Pdl(k′)+Wdl，i(k′)
Yj(k′)＝Hdl，j(k′)·Pdl(k′)+Wdl，j(k′)
y is abovei(k') is a downlink pilot signal received by the ith terminal, which is an N × 1 matrix, Hdl，i(k') is a downlink channel matrix from the base station to the ith terminal, which is an N × M matrix, Pdl(k ') is a downlink pilot signal, which is an M × 1 matrix, k' is a subcarrier number, Wdl，i(k') is the downlink channel noise from the base station to the ith terminal.
When the terminal employs N transmitting antennas, the number of CSI (channel state information) of downlink channels to be uploaded on each antenna of the terminal is shown in table 1 below.
Table 1:
because M × N correlation coefficients need to be fed back at each downlink pilot symbol of each terminal, and the terminal needs to feed back CSI on each receiving antenna, the resource occupied by the uplink common pilot channel of each terminal is N times of that of its downlink pilot.
If STC (space time coding) mode is adopted, including FDM mode: the density of the common pilot frequency on the frequency domain is N times; TDM mode: using N times OFDM symbol; the CDM method: and occupying N public code channels, feeding back the same information on each transmitting antenna of the terminal, wherein the fed back CSI is M multiplied by N.
If an SM (space division multiplexing) mode is adopted, N transmitting antennas are utilized, and the number of CSI fed back by each antenna is M.
The terminal multiplies the downlink pilot signal to be fed back by the orthogonal code and then superposes the downlink pilot signal with the uplink pilot signal of the terminal on the same time-frequency resource to obtain a mixed pilot signal.
The terminal modulates the mixed pilot signal and uplink data through OFDM, adds CP and sends the signal to the base station.
The downlink pilot frequency and the uplink pilot frequency should meet the following conditions:
1. convolution of uplink pilot frequency on time domain is LulWithin the range, an impulse function is defined, that is, the autocorrelation function of the uplink pilot frequency in the time domain is:
2. convolution of downlink pilot frequency on time domain is LdlWithin the range, an impulse function is defined, that is, the autocorrelation function of the downlink pilot frequency in the time domain is:
3. convolution of downlink pilot frequency and uplink pilot frequency on time domain is Lul+LdlIn the range zero, i.e.:
the design of the uplink and downlink pilot frequency meeting the above conditions can ensure that the base station can not generate interference between the uplink channel and the downlink channel in the estimation process of the uplink channel and the downlink channel. In a specific implementation, the above condition can be satisfied by:
1. the downlink pilot and the uplink pilot are orthogonal to each other. The uplink pilot sequence is the cyclic shift of the downlink pilot sequence, and the length of the cyclic shift is greater than the maximum time delay expansion of the channel.
2. The downlink pilot and the uplink pilot are orthogonal to each other. And respectively spreading the downlink pilot frequency and the uplink pilot frequency by using different orthogonal codes and then superposing the spread spectrum to obtain the mixed pilot frequency.
3. And after spreading the frequency of the downlink pilot frequency by using the orthogonal code, superposing the downlink pilot frequency to the uplink pilot frequency to obtain a mixed pilot frequency. Although the uplink and downlink pilots do not satisfy the above condition, the influence of the uplink pilots on the downlink channel estimation is approximately considered to be almost negligible as long as the spreading factor is large enough and the uplink pilot mean is designed to be zero.
When there are multiple terminals, the orthogonal codes of different terminals are orthogonal to each other. Therefore, the orthogonal code can be used to distinguish the downlink pilot signals of different terminals. The method for mutually orthogonalizing the orthogonal codes of different terminals may be as follows:
the orthogonal codes corresponding to other terminals are cyclic shifts of the orthogonal codes corresponding to the terminals, and the length of the cyclic shift is greater than the maximum time delay expansion of a channel; or, the orthogonal codes corresponding to other terminals and the orthogonal codes corresponding to the terminals are different spreading codes.
When there are multiple terminals, the uplink pilots of different terminals are also orthogonal to each other. The method for mutually orthogonalizing the uplink pilots of different terminals may be as follows:
the uplink pilot sequences of other terminals are cyclic shifts of the uplink pilot sequences of the terminals, and the length of the cyclic shifts is greater than the maximum time delay expansion of a channel; or, the uplink pilots of different terminals are spread by different orthogonal codes respectively.
The orthogonal code may be a walsh code, a CAZAC code, or the like.
In the following, for simplicity, it is assumed that the number of transmit antennas of the base station, the number of receive antennas, and the number of transmit antennas and receive antennas of the terminal are all 1, i.e. SISO system, and the following formula can be easily generalized to MIMO system, and the principle is consistent.
The processing procedure after the base station receives the data returned by the terminal in this embodiment is shown in fig. 4, and the specific processing procedure is as follows:
the signal transmitted by the terminal is transmitted through an uplink channel and then received by the base station. After the base station performs CP-removing and OFDM-demodulation on the received signal, the obtained mixed pilot signal is:
YBS(k)＝Hul，i(k)·(Yi(k′)·Cul，i(k)+Pul，i(k))+Wul，i(k)+Hul，j(k)·(Yj(k′)·Cul，j(k)+Pul，j(k))+Wul，j(k)
＝Hul，i(k)·Hdl，i(k′)·Pdl(k′)·Cul，i(k)+Hul，i(k)·Pul，i(k)+Wi(k)+
Hul，j(k)·Hdl，j(k′)·Pdl(k′)·Cul，j(k)+Hul，j(k)·Pul，j(k)+Wj(k)
Wi(k)＝Hul，i(k)·Wdl，i(k′)·Cul，i(k)+Wul，i(k)
Wj(k)＝Hul，j(k)·Wdl，j(k′)·Cul，j(k)+Wul，j(k)
wherein Y isBS(k) Superimposed signals of mixed pilot signals returned by a plurality of terminals received by a base station, Hul，i(k) For the uplink channel from the ith terminal to the base station, Pul，i(k) For the uplink pilot of the ith terminal, Cul，i(k) Orthogonal codes for distinguishing different users for the ith terminal. Wul，i(k) The uplink channel noise from the ith terminal to the base station.
The base station estimates the uplink channel first, and for YBS(k) Dot-by-dot on the frequency domain the conjugate of the uplink pilot:
Zul，i(k)＝YBS(k)·P* ul，i(k)
＝Hul，i(k)·Hdl，i(k′)·Pdl(k′)·Cul，i(k)·P* ul，i(k)+Hul，i(k)·Pul，i(k)·P* ul，i(k)+Wi(k)·P* ul，i(k)+
Hul，j(k)·Hdl，j(k′)·Pdl(k′)·Cul，j(k)·P* ul，i(k)+Hul，j(k)·Pul，j(k)·P* ul，i(k)+Wj(k)·P* ul，i(k)
since the uplink and downlink pilot signals of each terminal satisfy the above conditions, the estimation of the uplink channel is not affected by pilot aliasing. The uplink channel of the ith terminal estimated by the base station is:
then, the base station estimates the downlink channel based on the estimation result of the uplink channel, and Y is estimatedBS(k) Dot-multiplied conjugate of downlink pilot on frequency domain:
Zdl(k)＝YBS(k)·P* dl(k′)
＝Hul，i(k)·Hdl，i(k′)·Pdl(k′)·Cul，i(k)·P* dl(k′)+Hul，i(k)·Pul，i(k)·P* dl(k′)+Wi(k)·P* dl(k′)+
Hul，j(k)·Hdl，j(k′)·Pdl(k′)·Cul，j(k)·P* dl(k′)+Hul，j(k)·Pul，j(k)·P* dl(k′)+Wj(k)·P* dl(k′)
because the uplink and downlink pilot signals of each terminal satisfy the above conditions, the estimation of the downlink channel is not affected by pilot aliasing:
since the downlink channels of different users are distinguished by using the uplink orthogonal codes, the downlink channel of the ith terminal estimated by the base station is:
in practical applications, the estimation process of the uplink channel and the downlink channel may be improved as follows.
1. The MMSE channel estimation suppresses noise.
As can be seen from the above formulas for deriving the uplink channel and the downlink channel of the terminal, when estimating the uplink channel and the downlink channel, the noise therein includes: uplink channel noise and downlink channel noise. Therefore, after receiving the downlink pilot signal sent by the base station, the terminal may estimate the downlink channel at the downlink pilot by using an MMSE (minimum mean Square Error) channel estimation method, which may effectively suppress the downlink channel noise.
Downlink pilot signals received by the terminal:
Yi(k′)＝Hdl，i(k′)·Pdl(k′)+Wdl，i(k′)
estimating the downlink channel at the downlink pilot frequency by using MMSE channel:
Zi(k)＝Yi(k)·P* dl(k′)/|Pdl(k′)|2＝Hdl，i(k′)+Wdl，i(k′)·P* dl(k′)/|Pdl(k′)|2
then, the terminal multiplies the information of the downlink channel estimated at the downlink pilot frequency by an orthogonal code, and then superposes the information on the uplink pilot frequency to send to the base station. The improved method can improve the estimation performance of the uplink channel and the downlink channel.
2. And (5) compression coding.
In order to reduce the CSI feedback quantity of the terminal and reduce the resources occupied by the uplink common pilot of the terminal, the terminal can compress and encode the downlink channel information at the downlink pilot position needing to be fed back, and then multiply an orthogonal code and superpose the information on the uplink pilot.
3. The transmission is repeated.
In order to improve the estimation performance of the uplink channel and the downlink channel, if the number of the uplink pilots of the terminal is greater than the number of the downlink pilots, the mixed pilot signal may be transmitted repeatedly by using a plurality of uplink pilot resources, or the downlink pilots are encoded and then transmitted by using a plurality of uplink pilot resources, thereby ensuring that the mixed pilot signal is correctly received by the base station.
4. And feeding back the partial CSI.
When the terminal transmits the mixed pilot signal to the base station, the terminal may first only occupy a part of the bandwidth to transmit a part of the mixed pilot signal. Then, after a period of time, another part of bandwidth is occupied, and a part of mixed pilot signal is transmitted, that is, the mixed pilot signal is transmitted to the base station by adopting a frequency hopping mode, and the downlink can also transmit narrowband downlink pilot by adopting a frequency hopping mode.
Embodiment 2, this embodiment is mainly to reduce the damage to the orthogonality of the pilot frequency due to frequency selective fading, and when the bandwidth is greater than the coherent bandwidth, different frequency points of the signal after passing through the broadband wireless physical channel exhibit different fading characteristics, so that each part of the signal undergoes different attenuations, resulting in frequency selective fading.
The processing procedure for estimating the uplink channel and the downlink channel provided in this embodiment is as follows:
1. the base station generates downlink pilot frequency, performs Fourier transform processing on the downlink pilot frequency, then performs subcarrier mapping and IFFT transform processing, and then transmits the downlink pilot frequency after OFDM modulation and CP addition.
2. The downlink pilot frequency sent by the base station is received by the terminal, after the terminal passes through CP and OFDM demodulation, the obtained downlink pilot frequency is multiplied by an orthogonal code and then is superposed with the uplink pilot frequency which is processed by Fourier transform to obtain mixed pilot frequency, and the mixed pilot frequency is transmitted to the base station by the terminal.
3. The base station receives the mixed pilot frequency, and performs FFT, sub-carrier mapping and inverse Fourier transform on the mixed pilot frequency. Then, the uplink channel is estimated by using the uplink pilot firstly in the time domain, and since the uplink pilot and the downlink pilot satisfy the orthogonality condition in the time domain (one or a few OFDM symbols are approximately channel-constant), the estimation of the uplink channel is not affected by pilot aliasing and frequency selectivity.
4. And the base station estimates the downlink channel according to the estimated uplink channel information, the downlink pilot frequency which starts to be transmitted and the mixed pilot frequency.
Embodiment 3, this embodiment is mainly to reduce the damage to the orthogonality of the pilots caused by different scrambling codes in uplink and downlink. The processing procedure for estimating the uplink channel and the downlink channel provided in this embodiment is as follows:
1. the base station generates downlink pilot frequency, after Fourier transform processing is carried out on the downlink pilot frequency, sub-carrier mapping and IFFT transform processing are carried out, then OFDM modulation and CP addition are carried out, scrambling is carried out by using downlink user scrambling codes, and then the downlink pilot frequency is emitted.
2. The terminal receives the downlink pilot frequency sent by the base station, the terminal demodulates the downlink scrambling code, removes CP, OFDM demodulates the downlink pilot frequency, scrambles the downlink pilot frequency by the uplink user scrambling code, multiplies an orthogonal code, and then superposes the multiplied orthogonal code with the uplink pilot frequency processed by Fourier transform to obtain a mixed pilot frequency, and the terminal transmits the mixed pilot frequency to the base station.
3. And the base station receives the mixed pilot frequency, and performs FFT (fast Fourier transform), sub-carrier mapping and inverse Fourier transform on the mixed pilot frequency. Then, the uplink channel is estimated by using the uplink pilot firstly in the time domain, and since the uplink pilot and the downlink pilot satisfy the orthogonality condition in the time domain (one or a few OFDM symbols are approximately channel-constant), the estimation of the uplink channel is not affected by pilot aliasing.
4. And the base station estimates the downlink channel according to the estimated uplink channel information, the downlink pilot frequency which starts to be transmitted and the mixed pilot frequency.
Embodiment 4, which mainly aims to reduce the noise variance and the influence of frequency selective fading, provides a processing procedure for estimating an uplink channel and a downlink channel as follows:
1. the base station generates downlink pilot frequency, performs N times of narrow-band spread spectrum processing on each downlink pilot frequency, and then transmits the downlink pilot frequency after OFDM modulation and CP addition. The N-fold spread signal may be repeated a plurality of times.
2. The downlink pilot frequency sent by the base station is received by the terminal, the terminal estimates the channel at the downlink pilot frequency after the downlink pilot frequency is subjected to CP and OFDM demodulation, then performs despreading operation on the channel, obtains the despread channel and then performs spread spectrum by using a spreading code. Then, it multiplies an orthogonal code and superposes with the ascending pilot frequency to obtain the mixed pilot frequency, the terminal sends the mixed pilot frequency to the base station.
3. After receiving the mixed pilot frequency, the base station carries out despreading processing and then uses the uplink pilot frequency to estimate the uplink channel, and because the uplink pilot frequency and the downlink pilot frequency meet the orthogonality condition, the estimation of the uplink channel is not influenced by pilot frequency aliasing.
4. And the base station estimates the downlink channel according to the downlink pilot frequency which starts to be transmitted and the mixed pilot frequency.
The despreading operation can reduce the downlink noise variance to 1/sqrt (N) and can effectively resist frequency selective fading. Because the terminal carries out the uplink spread spectrum operation, the base station can still well estimate the information of the downlink channel even if the terminal distributes very low power to the received downlink pilot signal.
Embodiment 5, which mainly aims to reduce the influence of frequency selective fading, provides a processing procedure for estimating an uplink channel and a downlink channel as follows:
1. the base station generates downlink pilot frequency, and then the downlink pilot frequency is transmitted after OFDM modulation and CP addition. The downlink pilot frequency consists of a plurality of sequences, each sequence occupies a segment of narrow-band bandwidth, and the uplink pilot frequency and the downlink pilot frequency have the same number of sequences and are orthogonal in a one-to-one correspondence manner;
2. the downlink pilot frequency sent by the base station is received by the terminal, the terminal estimates the channel at the downlink pilot frequency after the downlink pilot frequency is subjected to CP and OFDM demodulation, then multiplies the channel by an orthogonal code, and obtains a mixed pilot frequency after the channel is superposed with the uplink pilot frequency, and the terminal transmits the mixed pilot frequency to the base station. The uplink and downlink pilot frequency consists of a plurality of sequences, each sequence occupies a segment of narrow-band bandwidth, the number of sequences contained in the uplink and downlink pilot frequency is the same, and the sequences are orthogonal correspondingly one by one;
3. after receiving the mixed pilot frequency, the base station estimates the uplink channel by using the uplink pilot frequency, and because the uplink pilot frequency and the downlink pilot frequency meet the orthogonality condition, the estimation of the uplink channel is not influenced by pilot frequency aliasing.
4. And the base station estimates the downlink channel according to the downlink pilot frequency which starts to be transmitted and the mixed pilot frequency.
The 4 modification methods described above in example 1 are also applicable to examples 2 to 5, and the 4 modification methods may be used in combination, and examples 1 to 5 may also be used in combination.
A schematic structural diagram of an embodiment of the channel information acquisition apparatus provided in the embodiment of the present invention is shown in fig. 5, and includes the following modules:
the pilot frequency sending and receiving module 51 is configured to send downlink pilot frequency information to a receiving end, receive a mixed pilot frequency returned by the receiving end, where the mixed pilot frequency is obtained by multiplying the received downlink pilot frequency by an orthogonal code, and then superimposing the multiplied downlink pilot frequency with an uplink pilot frequency orthogonal to the downlink pilot frequency, where the orthogonal code uniquely corresponds to the receiving end. The method comprises the following steps: a fourier transform processing module 511, a scrambling code processing module 512, a spreading processing module 513 or a segment transmission module 514.
A channel information obtaining module 52, configured to estimate uplink channel information according to the uplink pilot information in the mixed pilot, and estimate downlink channel information of the receiving end according to the estimated uplink pilot information and the downlink pilot and orthogonal code information in the mixed pilot.
The fourier transform processing module 511 in the pilot sending and receiving module 51 is configured to perform fourier transform on the downlink pilot, transmit the downlink pilot, receive a mixed pilot returned by the receiving end, perform inverse fourier transform on the mixed pilot, and obtain the mixed pilot by the receiving end after multiplying the downlink pilot by the orthogonal code and superimposing the mixed pilot with an uplink pilot that is subjected to fourier transform;
the scrambling code processing module 512 in the pilot frequency sending and receiving module 51 is configured to scramble the downlink pilot frequency with a downlink user scrambling code and then transmit the scrambled downlink pilot frequency, receive a mixed pilot frequency returned by the receiving end, perform uplink scrambling on the mixed pilot frequency, where the mixed pilot frequency is obtained by the receiving end performing downlink scrambling on the downlink pilot frequency, performing scrambling with an uplink user scrambling code, multiplying by the orthogonal code, and then superimposing on the uplink pilot frequency;
the spread spectrum processing module 513 in the pilot frequency sending and receiving module 51 is configured to perform spread spectrum processing on the downlink pilot frequency and then transmit the downlink pilot frequency, receive the mixed pilot frequency returned by the receiving end, perform despreading spectrum processing on the mixed pilot frequency, where the mixed pilot frequency is obtained by performing despreading spectrum processing on the downlink pilot frequency by the receiving end, performing spread spectrum processing on the downlink pilot frequency by using a spreading code, multiplying the downlink pilot frequency by the orthogonal code, and then superimposing the orthogonal code on the uplink pilot frequency.
The segment transmission module 514 in the pilot sending and receiving module 51 is configured to transmit the downlink pilot to the receiving end for multiple times, where each transmission occupies a part of downlink bandwidth, and sends a part of the downlink pilot.
The channel information acquiring apparatus may be a base station, and the fourier transform processing module 511, the scrambling processing module 512, the spreading processing module 513 or the segmentation transmission module 514 may be used in combination.
The schematic structural diagram of an embodiment of the pilot information processing apparatus provided in the embodiment of the present invention is shown in fig. 6, and includes the following modules:
and the hybrid pilot frequency acquisition module 61 is configured to receive downlink pilot frequency information sent by a transmitting end, multiply the downlink pilot frequency by an orthogonal code, and then superimpose the downlink pilot frequency and an uplink pilot frequency to obtain a hybrid pilot frequency, where the orthogonal code uniquely corresponds to the receiving end. The method comprises the following steps: a compression coding module 611 or a minimum mean square error channel estimation module 612.
A mixed pilot transmission module 62, configured to transmit the mixed pilot acquired by the mixed pilot acquisition module 61 to the transmitting end. The method comprises the following steps: at least one of the repeat transmission module 621 and the segment transmission module 622.
The compression coding module 611 in the hybrid pilot acquisition module 61 is configured to perform compression coding on the downlink pilot, multiply the downlink pilot by the orthogonal code, and superimpose the uplink pilot to obtain the hybrid pilot;
the minimum mean square error channel estimation module 612 in the mixed pilot frequency acquisition module 61 is configured to estimate a downlink channel of the downlink pilot frequency by using a minimum mean square error channel estimation method, multiply the information of the downlink channel by the orthogonal code, and obtain the mixed pilot frequency after superimposing the orthogonal code with the uplink pilot frequency. The method comprises the following steps: a repeat transmission module 621 or a segment transmission module 622.
The repeated transmission module 621 in the mixed pilot transmission module 62 is configured to repeatedly transmit the mixed pilot signal to the transmitting end by using multiple uplink pilot resources when the number of uplink pilots of the receiving end is greater than the number of downlink pilots, or transmit the mixed pilot signal by using multiple uplink pilot resources after coding the downlink pilots;
the segment transmission module 622 in the hybrid pilot transmission module 62 is configured to transmit the hybrid pilot signal to the transmitting end for multiple times, where each transmission occupies a part of the uplink bandwidth, and sends a part of the hybrid pilot signal.
The pilot information processing device may be a terminal. The compression coding module 611, the minimum mean square error channel estimation module 612, the repeated transmission module 621 and the segmented transmission module 622 may also be combined and used simultaneously.
In summary, the method and the apparatus of the embodiments of the present invention can enable the base station to correctly obtain the information of the uplink and downlink channels without the need of additionally opening up precious time-frequency resources for the uplink channel. And the terminal does not need to judge the precoding matrix, thereby greatly reducing the processing complexity of the terminal. And the damage to the orthogonality of the pilot frequency caused by frequency selective fading can be avoided, and the damage to the orthogonality of the pilot frequency caused by different scrambling codes of an uplink and a downlink can be avoided. The base station can realize more flexible scheduling according to the obtained complete downlink channel state information, and improve the system capacity.
The method and the device of the embodiment of the invention can be suitable for SISO systems and MIMO systems. The base station can perform pre-equalization processing or pre-coding processing according to the acquired channel information, can flexibly design a pre-coding matrix, and avoids precision reduction caused by limited number of codebooks. And the base station is favorable for flexibly allocating time-frequency resources to different services according to the channel information.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (20)
1. A method for obtaining channel information, comprising:
a transmitting terminal sends downlink pilot frequency information and receives a mixed pilot frequency returned by a receiving terminal, wherein the mixed pilot frequency is obtained by multiplying the received downlink pilot frequency by an orthogonal code and then overlapping the uplink pilot frequency by the receiving terminal, and the orthogonal code is uniquely corresponding to the receiving terminal;
and the transmitting terminal acquires uplink channel information according to the uplink pilot frequency information in the mixed pilot frequency, and acquires the downlink channel information of the receiving terminal according to the uplink channel information and the downlink pilot frequency and orthogonal code information in the mixed pilot frequency.
2. The method of claim 1, wherein the transmitting end sends downlink pilot information and receives the hybrid pilot returned by the receiving end, and specifically comprises:
and the transmitting end performs Fourier transform processing on the downlink pilot frequency, then transmits the downlink pilot frequency and receives the mixed pilot frequency returned by the receiving end, wherein the mixed pilot frequency is obtained by the receiving end by multiplying the downlink pilot frequency after the Fourier transform processing by the orthogonal code and then superposing the downlink pilot frequency after the Fourier transform processing and the uplink pilot frequency after the Fourier transform processing.
3. The method of claim 1, wherein the transmitting end sends downlink pilot information and receives the hybrid pilot returned by the receiving end, and specifically comprises:
and the transmitting end performs spread spectrum processing on the downlink pilot frequency, then sends out the downlink pilot frequency and receives a mixed pilot frequency returned by the receiving end, wherein the mixed pilot frequency is obtained by performing despread spectrum processing on the downlink pilot frequency after the spread spectrum processing by the receiving end, then performing spread spectrum processing on the downlink pilot frequency after the despread spectrum processing by using different spread spectrum codes, then multiplying the downlink pilot frequency by the orthogonal code and overlapping the orthogonal code with the uplink pilot frequency, and the transmitting end performs despread spectrum processing on the mixed pilot frequency.
4. The method of claim 3, wherein the performing the spread spectrum processing on the downlink pilot specifically comprises:
and performing narrow-band spreading on the downlink pilot frequency near the subcarrier where the downlink pilot frequency is located, and repeating the operation on the whole bandwidth to generate the spread downlink pilot frequency.
5. The method of claim 1, wherein the transmitting end sends downlink pilot information and receives the hybrid pilot returned by the receiving end, and specifically comprises:
the transmitting terminal scrambles the downlink pilot frequency by using a downlink user scrambling code and then transmits the downlink pilot frequency, receives the mixed pilot frequency returned by the receiving terminal, wherein the mixed pilot frequency is obtained by the receiving terminal by descrambling the downlink scrambling code on the downlink pilot frequency, scrambling the downlink pilot frequency by using an uplink user scrambling code, multiplying the scrambled downlink pilot frequency by the orthogonal code and then superposing the orthogonal code with the uplink pilot frequency, and the transmitting terminal performs uplink scrambling code descrambling on the mixed pilot frequency.
6. The method of claim 1, wherein the sending downlink pilot information by the transmitting end specifically comprises:
the transmitting terminal sends the downlink pilot frequency out for multiple times, each time of sending occupies partial downlink bandwidth, and partial downlink pilot frequency is sent respectively.
7. A method for processing pilot information, comprising:
receiving downlink pilot frequency information sent by a transmitting terminal, multiplying the downlink pilot frequency by an orthogonal code, and then superposing the downlink pilot frequency with an uplink pilot frequency to obtain a mixed pilot frequency, wherein the orthogonal code is uniquely corresponding to the receiving terminal;
and sending the mixed pilot frequency to the transmitting end.
8. The method of claim 7, wherein the downlink pilot and the uplink pilot are orthogonal to each other.
9. The method of claim 8, wherein the uplink pilot sequence is a cyclic shift of the downlink pilot sequence, and a length of the cyclic shift is greater than a maximum delay spread of a channel.
10. The method of claim 8, wherein the multiplying the downlink pilot by the orthogonal code and then superimposing the downlink pilot and the uplink pilot to obtain the hybrid pilot specifically includes:
and after spreading the downlink pilot frequency and the uplink pilot frequency by different orthogonal codes respectively, superposing the downlink pilot frequency and the uplink pilot frequency to obtain a mixed pilot frequency.
11. The method of claim 7, wherein the step of multiplying the downlink pilot by an orthogonal code and then superimposing the downlink pilot and the uplink pilot to obtain a hybrid pilot comprises:
and after the downlink pilot frequency is spread by using an orthogonal code, the downlink pilot frequency is superposed on the uplink pilot frequency to obtain a mixed pilot frequency.
12. The method of claim 7, wherein when there are multiple receivers, the orthogonal codes corresponding to different receivers are orthogonal to each other, and the uplink pilots of different receivers are orthogonal to each other.
13. The method of claim 12, wherein the orthogonal codes corresponding to different receiving ends are orthogonal to each other, and specifically comprising:
orthogonal codes corresponding to different receiving ends mutually form cyclic shift, and the length of the cyclic shift is greater than the maximum time delay expansion of a channel;
or,
the orthogonal codes corresponding to different receiving ends are different spreading codes respectively.
14. The method as claimed in claim 12, wherein the uplink pilots of different receiving ends are orthogonal to each other, specifically comprising:
the uplink pilot sequences of different receiving ends mutually form cyclic shift, and the length of the cyclic shift is greater than the maximum time delay expansion of a channel;
or,
the uplink pilot frequencies of different receiving ends are respectively spread by different orthogonal codes.
15. The method according to any one of claims 7 to 14, wherein the sending the hybrid pilot to the transmitting end specifically comprises:
the receiving end repeatedly transmits the mixed pilot signal by using a plurality of uplink pilot resources, and the number of the uplink pilots of the receiving end is greater than the number of the downlink pilots;
or,
the receiving end transmits the mixed pilot signal by using a plurality of uplink pilot resources after coding the downlink pilot, and the number of the uplink pilots of the receiving end is greater than that of the downlink pilot;
or,
and the receiving end sends the mixed pilot signal to the transmitting end for multiple times, each time of sending occupies part of the uplink bandwidth, and part of the mixed pilot signal is sent respectively.
16. A channel information acquisition apparatus, comprising:
the pilot frequency sending and receiving module is used for sending downlink pilot frequency information to a receiving end and receiving mixed pilot frequency returned by the receiving end, wherein the mixed pilot frequency is obtained by multiplying the received downlink pilot frequency by an orthogonal code and then overlapping the multiplied downlink pilot frequency with uplink pilot frequency by the receiving end, and the orthogonal code is uniquely corresponding to the receiving end;
and the channel information acquisition module is used for acquiring uplink channel information according to the uplink pilot frequency information in the mixed pilot frequency and acquiring the downlink channel information of the receiving end according to the uplink channel information and the downlink pilot frequency and orthogonal code information in the mixed pilot frequency.
17. The channel information acquiring apparatus of claim 16, wherein the pilot transmitting and receiving module comprises: a Fourier transform processing module, a scrambling processing module, a spread spectrum processing module or a segmented transmission module, wherein,
the Fourier transform processing module is used for sending the downlink pilot frequency after carrying out Fourier transform processing on the downlink pilot frequency, receiving the mixed pilot frequency returned by the receiving end, and carrying out inverse Fourier transform on the mixed pilot frequency, wherein the mixed pilot frequency is obtained by the receiving end after multiplying the downlink pilot frequency subjected to the Fourier transform processing by the orthogonal code and superposing the downlink pilot frequency subjected to the Fourier transform processing and the uplink pilot frequency subjected to the Fourier transform;
a scrambling code processing module, which is used for scrambling the downlink pilot frequency by using a downlink user scrambling code and then transmitting the scrambled downlink pilot frequency, receiving the mixed pilot frequency returned by the receiving end, and performing uplink scrambling code removal on the mixed pilot frequency, wherein the mixed pilot frequency is obtained by performing downlink scrambling code removal on the downlink pilot frequency by the receiving end, performing scrambling by using an uplink user scrambling code, multiplying by the orthogonal code, and then overlapping with the uplink pilot frequency;
a spread spectrum processing module, configured to send out the downlink pilot frequency after performing spread spectrum processing on the downlink pilot frequency, receive a mixed pilot frequency returned by the receiving end, perform despread spectrum processing on the mixed pilot frequency, where the mixed pilot frequency is obtained by performing despread spectrum processing on the downlink pilot frequency after the spread spectrum processing by the receiving end, multiplying the downlink pilot frequency after the despread spectrum processing by the orthogonal code after performing spread spectrum processing by using different spreading codes, and superimposing the orthogonal code on the uplink pilot frequency;
and the segmented transmission module is used for transmitting the downlink pilot frequency to the receiving end for multiple times, each transmission respectively occupies partial downlink bandwidth, and partial downlink pilot frequency is respectively sent.
18. A pilot information processing apparatus, comprising:
the mixed pilot frequency acquisition module is used for receiving downlink pilot frequency information sent by a transmitting end, multiplying the downlink pilot frequency by an orthogonal code, and then superposing the downlink pilot frequency with an uplink pilot frequency to obtain a mixed pilot frequency, wherein the orthogonal code is uniquely corresponding to the receiving end;
and the mixed pilot frequency transmission module is used for sending the mixed pilot frequency acquired by the mixed pilot frequency acquisition module to the transmitting end.
19. The apparatus of claim 18, wherein the hybrid pilot acquisition module comprises: a compression coding module or a minimum mean square error channel estimation module, wherein,
a compression coding module, configured to perform compression coding on the downlink pilot frequency, multiply the downlink pilot frequency by the orthogonal code, and superimpose the orthogonal code with an uplink pilot frequency to obtain the hybrid pilot frequency;
and the minimum mean square error channel estimation module is used for estimating a downlink channel of the downlink pilot frequency by adopting a minimum mean square error channel estimation method, multiplying the information of the downlink channel by the orthogonal code, and superposing the orthogonal code with the uplink pilot frequency to obtain the mixed pilot frequency.
20. The pilot information processing apparatus of claim 18 or 19, wherein the hybrid pilot transmission module comprises: a repetitive transmission module or a segmented transmission module, wherein,
a repeated transmission module, configured to repeatedly transmit the mixed pilot signal to the transmitting end by using multiple uplink pilot resources when the number of uplink pilots of the receiving end is greater than the number of downlink pilots, or transmit the mixed pilot signal by using multiple uplink pilot resources after coding the downlink pilots;
and the segmented transmission module is used for transmitting the mixed pilot signal to the transmitting terminal for multiple times, each transmission respectively occupies partial uplink bandwidth, and partial mixed pilot signal is respectively transmitted.
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| CNA2008101058502A CN101572682A (en) | 2008-05-04 | 2008-05-04 | Method and device for acquiring channel information |
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| CNA2008101058502A CN101572682A (en) | 2008-05-04 | 2008-05-04 | Method and device for acquiring channel information |
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